Data collection in a large-scale network with specified low-power radio stations (Article 6(4) (ii) of the Enforcement Regulations for the Radio Act) has been studied. The data collection in a large-scale network is exemplified by telemetering, in which the amount measured in a remote place is transmitted to be displayed or recorded in another place, or monitoring in a large-scale factory.
The physical layer (PHY) and the medium access control (MAC) layer specified in IEEE 802.15.4 are used for the above network. The network is configured as a wireless multi-hop network, and can collect pieces of data from a large number of terminals that exist over a wide area.
An ad hoc network or a mesh network is included in the wireless multi-hop network.
In the communication between a wireless master station and a wireless slave station, the wireless multi-hop network can autonomously select and use, in accordance with a transmission environment, a transmission route through which the wireless master station and the wireless slave station directly communicate with each other or a transmission route through which the wireless master station and the wireless slave station communicate with each other via another wireless slave station.
In a star network in which the wireless master station and the wireless slave station communicate on a one-to-one basis, the transmission route between the wireless master station and the wireless slave station is fixed. Therefore, the quality of communication is degraded or communication is disabled as soon as the transmission environment is deteriorated.
In contrast, the wireless multi-hop network enables communication through a bypass transmission route, that is, communication via another wireless slave station. Therefore, communication can be continued even when the transmission environment is deteriorated.
In addition, in a case where the wireless multi-hop network has a large number of wireless slave stations, a plurality of options for transmission routes can be obtained. Therefore, redundancy of transmission routes is achieved, and the quality of communication can be stabilized.
Due to the above characteristics, the actual transmission routes in the wireless multi-hop network depend on the number of wireless slave stations, an installation environment, and the transmission environment. Therefore, it is difficult to determine the communication cycle.
As a related technique, following Patent Literature 1 describes a transmission environment evaluation device including an operation terminal, a wireless master station, and a plurality of wireless terminals. Specifically, configurations of communication routes are concurrently switched to the set configurations at the timing designated by the operation terminal. After that, parameters such as a route for measuring a transmission path environment and a repetitive measuring execution cycle are set, and the measurement is performed (paragraphs 0039 to 0052).
In addition, following Patent Literature 2 describes a multi-hop wireless network in which an information distribution server controls the size of data and data transmission intervals in accordance with an effective transmission rate and the total number of connected terminals (paragraphs 0056 to 0058).